Pyrolysis of c-acetoxy aliphatic amides to acrylamides



Patented Jan. 17, 1950 PYROLYSIS F C-ACETOXY ALIPHATIC v All/ IDES r0ACRYLAMIDES William P. Ratchford, Philadelphia, and Charles H. Fisher,Abington, Pa., assignors to the United. States of America as representedby the Secretary of Agriculture No Drawing. Application April 16, 194.6,

- Serial No. 662,438

6 Claims.

(Granted under the am March a, 1883, as amended April so, 1928; 370 o.G. 757)" This application is made under the act of March 3, 1883, asamended by the act of April 30, 1928, and the invention hereindescribed, it patented, may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment to us of any royalty thereon.

This invention is related to the preparation and utilization ofunsaturated amides, particularly acrylamides having the formula CH2 1 C(R) CONRR' wherein R is hydrogen or alkyl and R is alkyl.

Unsaturated amides previously have been made by various methods thathave certain disadvantages. However, satisfactory methods for convertinghydroxy amides into the corresponding unsaturated amides had notbeen'known.

We have found. that hydroxy amides may be transformed into usefulunsaturated amides by acylation followed by thermal decomposition. Wehave found, moreover, that hydroxy amides may 1,4588) was 86 per cent.Anal. calcd. for

.C5H1102N2 N, 11.96; M 30.77. Found: N, 11.77;

In subsequent preparations in which sulfuric acid was not used, yieldsof 89 percent and 83 percent, respectively, were obtained by allowing be'acylated with various agents, "including cari boxylic acids, acidchlorides, acid anhydrides.

ketene and certain esters. .In addition, we have converted theunsaturated amides obtained by pyrolysis of acyloxy amides into usefulpolymers, copolymers, and other products.

The .acrylamides polymerize readily by methods already known in the art.Mass polymerization, for example, was achieved by-allowing theacrylamides containing small quantities of benzoyl peroxide to stand atroom temperature for several days: Mass polymerization occurred morerapidly at 60 to .80" -C.. A convenient method of. polymerizing thelower acrylamides comprises heating an aqueous solution containingapproximately 5 percent to 40 percent of the amide and a small quantityof ammonium. persulfate at about 60 to 90 :C. Other solvents andcatalysts may be usedfor. the polymerization.

The acrylamides copolymerize readily with acrylic esters, methacrylicesters, styrene, and other unsaturated monomers of the vinyl type. Ourinvention is illustrated, but not by the following examples:

Example I .(MN-dimethyllactamide) A mixture of 1.5 moles methyl lactate,1.5 moles dimethylamine, and 5 drops concentrated sulfuric limited,

acid was allowed to-stand in a closed bottle at room temperature for 3weeks. Thesulfuric acid was neutralized with sodium acetate, and theresulting mixture was distilled. The yield of. amide (B. P. 56 to 57":(0.6 mm.); d4, 1.0508; n

'Dean and Stark tube.

the methyl lactate-dimethylamine mixture to stand at room temperaturefor three weeks and at about 30 for 24 hours.

Example II.-N,N-(dimethyl-alphaacetozrypropz'onamide) Thedimethyllactamide (2.4 moles) 10 percent excess acetic anhydride, and0.3 ml. concentrated sulfuric acid were mixed, and then heated on asteam bath; the temperature (exothermic reaction) went to The sulfuricacid was neutralized with anhydrous sodium acetate, and

the mixture was distilled (97 percent yield;- B. P. 67.5 (0.3 mm); d41.0681; n ,'1.4530. The distillate solidified (M. P., 44-6") Anal.calcd. for C7H13O3N; N, 8.80; saponification equivu' 159.2; M 40.13.Foundz N, 8.81; saponification equiv., 159.8; M 4021;

Example III A mixture of 1 mole dimethyllactamide, 4 moles acetic acid,200 ml. benzene, and 0.5 ml. concd.

sulfuric acid was refluxed 27hours, 10 g. aqueous layer (containing 5 g.H2O) being obtained in the the mixture yielded 0.74 mole unreactedhydroxy amide and 0.12 mole (48 percent yield) acetoxy amide.

7 Example IV To 1 mole N,N-dimethyllactamide containing 1 g. KCN wasadded slowly (heating and stirring) 1 mole vinyl acetate. When aboutone-half of the vinyl acetate had been'added the mixture warmedspontaneously, requiring cooling. At the-end of the addition of vinylacetate, the mixture was heated to 65 and allowed to standovernight.

The mixture was distilled, giving 0.47 mole unreacted amide and 0.50mole acetoxyamide (94 percent yield).

Example V Ketene prepared bypyrolizing acetone in a ketene lamp waspassed through 1 mole of dimethyllactamide at room temperature forapproximately 12 hours. Upon distillation, 0.28 mole unreacted amide and0.55 mole ('76 percent yield) acetoxy amide were obtained.

The catalyst was neutralized with sodium acetate. Upon distillation,

Example VI The acetoxy amides were pyrolized by passage through avertical Pyrex-glass tube (approximately 1 inchin diameter) heated overa length.

of approximately 15 inches. The acetoxy amides were pumped into the topof *the tubezaand the products were collected in a cooled receiver atthe bottom of the pyrolysis tube: A small quantity of polymerizationinhibitor (usually hydroqui none) was added to the condensate, and themesuiting mixture was then distilled to recover the acrylamide. Dataobtained by pyroli-zing N,N-.-

dimethyl-alpha-acetoxypropionamide are given below in the table.

Treatment of N,N-diethy1lactamide with acetic anhydride" in the= mannerdescribed above for N;N-'di'ethylia;etamide yielded N ,N-diethyl-alphaacetoxypropienamide.

Example IX Acetoxypropionyl chloride (22 moles) was allowed to reactwith 2 moles diethylamine. N-di- Table-Pyrolysis ofN,N-dimethylalpha-acetoxypropionamide Yield, percent of theoreticalExpt. Gms." Temp: g gg igg k Acetic acid" No. pyrolyzed 0. secs! moles/mg l g1 I V amide 'Iitra- Distillatien tion' 1 Basedon theiree spaceinthepyrolysistube within 15 temperature.

i Oirthe'basls oi unrecoveredaacetoxy amide;

were 82 to 98% The ldirnethylacrylamideiwfraction '-obtained bydistillation1.-of.-.-the .pyrolyzates contained acetic aQ-ida:Although-:this' fraction :iszuseful for poly-1 mer-iz-ation. and.otherzpurposes the acetic acid may be. removed-bytreatment withsodium carbonate-or other alkaline materials.

A satisfactory method ofi-puriffing theidimethylacrylamide comprisedtreating the acidic amide fraction with either excessan'hydrous sodiumcarbonate, or stheztheoreticalaquantity; of 50 percent queous sodiumhydroxide; filtering. anddistilling them-filtrate 1(ih117he.presencezliof hydro uinane) ndeltzreducedzpressure. Tlie recovery.ofidimeth ylacrylami-de:la(containing about 2 percent acid) afterrone;.suchitreatmentwwaszapproximately 70 percent-.- Dimethylacrylamide=1obtained by the complete removal.ofsacidiciimpuritiesfollowed byredistillation had properties (B. P. 735 to 73. 4 at 16.5 mm.; d40.9651; n Q 1.4732; M 28.81; N, 14.25 (theoretical, 14.1'3'percent)),similar tozthoses of the amide prepared -from' acrylyl chloride-anddimethylamine...

Example "VII" 0.34moleof N,N.-diethyllactamide was prepared aasfollows-z A mixture of :polylactic acid; in amount equivalenttoziimole; ofclactic acid, 'and:the de-L greeof polymerization. of; which:was approxi-e mately: '1 1,- 'WfiS-01'6fil1X6d5Wibhi:IL.1 .molediethylsamine for 11 hours and heated in a sealedccon -z Y currentlythrough a heated towereipacked with;

small porcelain Berl saddles). In difierent exof the stated pyrolysis aNot corrected for aceticacid (approximately 15% by Weight); eorrectedyieldsaethylacetoxypropienamide rwasaobtained in "66;"

percent yield by: distillatiodpf the 'reaction' mii'c- VI; yielded= N ,Ndiethylacrylamide in good yield.

A mixture of 2 moles methykwlphmhydroxyiso butyrate; -2molessmethylaminegan'd 0.2 m1. concentrated: sulfuric; acidswasiallowedi'to stand at room ten'iperature' for 2 months-. The sulfuricacid was neutralized with an'hydrous sodium acetate; and "themixture' iwas distilled (yield, 97*

The hydroxy amidewas acetylated with; 10 percent excessecetic anhydride;using concentrated sulfuric acid as catalyst? 1 After 'the 'catalyst wasneutralized-wand the acetic F acid dist'illed; the acetoxy amide wascollected at' 8/ a3; n 1.45352 Theyield was fibpercentfwith' formationof viscous; tack-y fractions.

N-methylacetdxyisobutyramide ('95 e. in 81 g.

benzene) was pyrolyzed-at-476 at therate of 0.842"- mole perhouricontacttime-"1.22%sec.). Distillation of the =pyrolyzate-yieldedN-methylm'ethacrylamide.

Exampie Xla- Prpafidtidk "and pyrolysis of -'N,N-

dimethyL-alpfia-acetaxyisobutyramine Usingtmeth'ods deseribedahov'egmN-dimethylmetha'crylamide:= was" prepared. Treatment ofalpha-acetowisobutyryl fchioride 'with "dimethyl amine yielded'=-N,N-dimethyP alpha-acetoiiyiso butYramidBL- A sammeaq 0:92 ofthis'amidedisf solved in 81-g. beiizerie was pyrolyzed at 480 C.

(contact time, 1.7 seconds). Upon distillation of the pyrolyzate,N,N-dimethylmethacrylamide was obtained in high yield.

Example XIL To 3.5 g. of N,N-dimethylacrylamide was added 0.018 g.benzoyl peroxide. After the mixture was exposed to sunlight, theacrylamide polymerized to a colorless transparent resin. In a similarway, resins were prepared from N,N-diethylacrylamide.

Example XIII To a per cent aqueous solution of N,N-dimethylacrylamidewas added 0.5 percent (by weight of monomer) of ammonium persulfate. Thesolution was heated gently. At 70 C. polymerization took place, forminga viscous solution.

When a 20 percent aqueous solution of N,N-dimethylacrylamide waspolymerized under the same conditions, the resulting polymer gelled.

Using a similar technique, N,N-diethylacrylamide was polymerized inaqueous solution. This polymer, it was found, was less soluble in hotwater than in cold.

Example XIV (Pyrolysis) CQHfiG O O CH(CH3) CHzC ON(CH3):N,N-dimethyl-beta-benzoyloxybutyramide CH;CH CHO ON(CH|): COHIC O OHN,N-dimethylcrotonamide Benzoic acid (Pyrolysis) C13 0 O O OH(CHB)CH(CH;) C ONHCH; --r N-methyl-beta-acetoxy-alpha-methyl-butyramide CHQCHC(CH C ON'HCH; OHSC O OH N-methyl-alpha-methylcrotonamide Acetic acidHaving thus described our invention, we claim:

1. The process of preparing N,N-dimethylacrylamide, which comprisesthermally decomposing N,N dimethyl alpha acetoxypropionamide to removethe acetoxy group and a hydrogen atom on the carbon atom adjoining thecarbon atom to which the acetoxy group is attached at about 476 to 559C.

2. The process of preparing N,N-diethylaorylamide, which comprisesthermally decomposing N,N-diethylealpha-acetozwpropionamide to removethe acetoxy group and a hydrogen atom on the carbon atom adjoining thecarbon atom to which the acetoxy group is attached at about 476 to 559C.

3. The process of preparing N-methyl-methacrylamide of the formula CH2 2C (CH3) CONH(CH3) which comprises thermally decomposing N-methyl-alpha-acetoxyisobutyramide to remove the acetoxy group and ahydrogen atom on the carbon atom adjoining the carbon atom to which theacetoxy group is attached at about 476 to 559 C.

4. The process of preparing an N-lower alkyl amide of an alpha-betaunsaturated aliphatic carboxylic acid comprising pyrolyzing an N-loweralkyl amide of a C-alkanoyloxy lower fatty acid having more than twocarbon atoms, the alkanoyloxy group being in one of the positions alphaand beta, the other of the positions alpha and beta having a hydrogenatom, the C-alkanoyloxy group being a lower group, the N-lower alkylradical being taken from the group consisting of -Jower alkyl andN-(lower-alkyDz, at about 476 to about 559 C.

5. The process of preparing an N-di-lower alkyl amide of acrylic acidcomprising pyrolyzing an N-di-lower alkyl amide of alpha-acetoxypropionic acid at about 476 to 559 C.

6. The process of preparing an HN-lower alkyl amide of methacrylic acidcomprising pyrolyzing an HN-lower alkyl amide of alpha-acetoxyisobutyricacid at about 476 to 559 C.

WILLIAM P. RATCHFORD. CHARLES H. FISHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,986,854 Reid Jan. 8, 19352,183,357 Ritchie et a1 Dec. 12, 1939 2,208,328 Lichty July 16, 19402,231,905 Hanford et al Feb. 18, 1941. 2,265,814 Ritchie et a1. Dec. 9,1941 2,288,197 Kranzlein et a1. June 30, 1942 2,301,131 Lichty NOV. 3,1942 2,311,548 Jacobson Feb. 16, 1943 2,320,089 Lichty May 25, 19432,375,005 Kung May 1, 1945 2,401,885 Semon June 11, 1946

4. THE PROCESS OF PREPARING AN N-LOWER ALKYL AMIDE OF AN ALPHA-BETAUNSATURATED ALIPHATIC CARBOXYLIC ACID COMPRISING PYROLYZING AN N-LOWERALKYL AMIDE OF A C-ALKANOYLOXY LOWER FATTY ACID HAVING MORE THAN TWOCARBON ATOMS, THE ALKANALYLOXY GROUP BEING IN ONE OF THE POSITIONS ALPHAAND BETA, THE OTHER OF THE POSITIONS ALPHA AND BETA HAVING A HYDROGENATOM, THE C-ALKANOYLOXY GROUP BEING A LOWER